Apparatus for forming sealed lap seams



Jan. 13, 1953 .1. HERMAN APPARATUS FOR FORMING SEALED LAP SEAMS FiledNov. 12, 1948 0 7g erzrzarz,

Jan, 13, 1953 J. HERMAN APPARATUS FOR FORMING SEALED LAP SEAMS m m w s\mu llHl Filed Nov. 12, 1948 Patented Jan. 13, 1953 APPARATUS FOR FORMINGSEALED LAP SEAMS John Herman, Chicago, Ill., assignor to J. W. JohnsonCompany, Chicago, 111., a corporation of Illinois Application November12, 1948, Serial No. 59,633

11 Claims.

This invention relates to apparatus for forming sealed lap seams infabric objects, and in particular it relates to an attachment for heavyduty sewing machines by means of which a sealing strip formed of aflowable solid elastomer may be continuously laid between theoverlapping adjacent layers of fabric in such a way as to seal the linesof stitching.

In the making of waterproof fabric objects, and in particulartarpaulins, it is customary to employ a plurality of pieces of heavywaterproofed material, such as canvas, and the seams of a tarpaulin arecustomarily simple lap seams with a double line of stitching securingthe lapped edges together.

It is obvious that in stitching the seam, either by hand or with asewing machine, the needle holes which are necessarily in register inthe lapped layers of fabric leave numerous small holes through whichwater can pass, particularly where there is standing water on thesurface of the tarpaulin.

I have discovered that the common lap seam in a tarpaulin may berendered waterproof by placing a sealing strip composed of a flowable'solid elastomer between the overlapping edge portions of the fabric andstitching through the elastomer. The elastomer may then be flowed closeabout the threads so as to seal the needle holes by applying pressure tothe completed seam,

as with a presser roll.

The improved waterproof fabric object and method of m-aking'it aredescribed and claimed in my copending application, Serial No. 59,634,filed November 12, 1943.

In commercial operation it is necessary to employ heavy duty sewingmachines of the double chain stitch or look stitch type in order tostitch the adjacent pieces of waterproof fabric together. Such machinesare usually furnished with a fabric guide ahead of the stitcher head bymeans of which two pieces of fabric may be guided to the stitcher headwith their seam forming edges in overlapping relationship. The fabric isdrawn through the stitcher head by means of a puller.

wheel unit immediately behind the stitcher head, the two pullerwheels'being provided with deep lateral cuts on their circumferentialsurfaces so as to make frictional engagement with the fabric. In theconventional commercial machine, the puller wheels are flat-toothed gearwheels.

My apparatus is provided with a fabric guide plate which is so arrangedas to guide the continuous strip of elastomer to the stitcher headbetween the lapped edge portions of the fabric.

In. order to apply the necessary pressure to the completed seam was toflow the elastomerclose about the threads, I substitute for theconventional puller wheel unit a presser roll unit in which the rollshave lightly scored surfaces so as to exert substantially uniformpressure upon all parts of the seam.

The apparatus is illustrated in a preferred embodiment in theaccompanying drawings in which:

Fig. 1 is a fragmentary and elevational view of a sewing machineprovided with the special fabric guide and modified roller;

Fig. 2 is a fragmentary front elevation thereof; m Fig. 3 is a plan viewof the fabric guide assem- Fig. 4 is a section taken as indicated at 4-4of of Fig. 3; and.

Fig.5 is a front elevation of. one element of the fabric guide assembly.

Referring to the drawings in greater detail, a work table, indicatedgenerally at 5, has secured to its top a sewing machine of the typecustomarily 'used in making tarpaulins or other heavy waterproof fabricobjects which is provided with an extremely long horizontal arm so as toaccommodate wide pieces of fabric. A vertical housing indicatedgenerally at 6 supports a reciprocating needle shaft 1 which is drivenin the customary fashion, and a retractable presser foot rod 8 to whichis secured a pressure foot 9. The, entire needle shaft 1, which in thistype machine carries two laterally spaced needles 10, may be raised fromthe work surface by means of a projecting lever H; and the retractablepresser foot may be raised by means of the lever 12. The combination ofthe presser foot '8 and needles I!) form a' stitcher head throughwhich-fabric passes in the process of having a seam stitched therein.

A support arm I3 secured to the vertical housing 6 carries a verticalsleeve I4 in which a shaft [5 is slidably mounted. 'A fork I6 is securedto the lower end of the shaft, and the entire shaft assembly may bemanually raised and lowered by means of a lever H, the shaft normallybeing urged toward its lower position by a coil spring I8 which iscoiled around the upper end of the shaft and confined between the topsurface of the support arm 13 and an upper spring stop (no shown).

The assembly so far described is common to all heavy duty machines ofthe type employed in making tarpaulins. Fabric is drawn through thestitcher head by a presser roll unit which includes a driven roll l9aprojecting through an aperture in the top of the work table top 5, andan idler roll 19 which is spindled in the fork (6, at 20, so as to bespaced slightly from the driven roll i912 and urged toward said roll bythe spring IS. The drive mechanism for the roll 19a is conventional,and. is not illustrated. As best seen in Fig. 2, the circumferentialsurface of the roll is is lightly scored, as at 2|, so as tofrictionally engage the surface of the fabric; and the circumferentialsurface of the driven roll We is also lightly scored.

A fabric guide assembly, indicated generally at 22, is secured to thework table immediately forward of the stitcher head by means of a pairof screws 23 extending through a slot 24 in a support element 25thereof.

The guide assembly comprises three superposed guide slots 26, 21 and 28,the lower slot 28 preferably having its bottom face formed by the top ofthe work table 5. The superposed guide slots 26, 27 and 28 receive,respectively, the upper piece of fabric A, the sealing strip, or tapeB,v and the lower piece of fabric C. The physical elements of the guideassembly, which form the slots 26, 2? and 28, will now be describedindetail.

As best seen in Figs. 3 and 4, a main plate, indicated generally at 29,includes a connector portion 30, and an L-shaped separator plate havinga first arm 31 at right angles to the path of travel of the fabricthrough the slots and a second arm 32 forming the lower surface of thecenter slot 21 which is a tape take-off slot. Thearms 31 and 32 are ofsuitable Width to accommodate the sealing tape B, and the outer cornerof the L is mitered', at 33, and provided with a spaced guide bar 34;while a. flat guide loop 35 is spaced from the lower surface. of the arm3! Thus, the supply roll (not shown) of tape B may be hung below thetable 5, forwardly and to one side of the stitcher head, and the tapemay be guided through the loop 35 which holds it close against theunderside of the arm 3|, between the mitered surface 33 and the guidebar 34, and along the upper side of arm 32 into the take-off slot 21.Therefore, as best seen in Fig. 2, the tape B is separated by the arm 3|from the immediately adjacent, overlying piece of fabric A while it ismoving across the line of travel thereof.

A spacer plate 36 forms the top surface of thetake-off slot 21, and hasan extending portion 31 provided with apair of parallel upstandin lugs38 which form a guideway for a slidable sideguide member 39. The member39 is. slotted at 4D to receive a retaining screw 4| by which it may beadjustably secured to the extending portion 37 of the spacer plate 35.The side guide member 39 forms the vertical guide surface of the upperfabric slot 26, and the adjustment of it permits variation in theoverlap between the sealing tape B and the upper fabric piece A.

As best seen in Figs. 4 and 5, a serpentine plate 42 has a lower element4-3- which serves as-the top surface of the lower guide slot 28, and adownwardly directed edge portion M of the serpentine plate forms thevertical guide surface of said slot. The serpentine plate curves outsidethe extension portion 3! of the spacer plate 36, and its upper element45 rests upon the side-guide member 39 to form the top surface of theupper slot 26. The extreme end portion of the serpentine plate G2 isreversely curved, as seen at 45, to form a handle and finger rest. Anaperture a in the upper element 45 gives access to the screw ii topermit adjustment of the side guide member 39.

The forward side of the principal convolution of the serpentine plate 42closed by an integral face plate 4? which is slotted at 48' to receive ascrew 49 by which the plate is secured to the extension portion 37 ofthe spacer plate 36. Thus, the serpentine plate is laterally adjustablewith respect to the main plate 29, and the adjustment permits variationin the overlap of the sealing tape 13 and lower fabric piece C.

In operation, the loose end of a roll of sealing tape is introducedbetween the first arm 31 of the separator plate and the guide loop 35,the tape is fed between the miter-ed edge 33 and guide bar 34 and thenceinto the take-on" slot 27. The piece of fabric A is placed in the upperguide slot 26 with its edge riding against the sideguide member 39, andthe piece of fabric C is introduced into the guide slot 23 with its edgeriding. against the vertical guide surface 44. The fabric pieces A and Care thus guided to the stitcher head with their seam forming edgeportions in over-lapping relationship and with the sealing strip Binterposed thercbetween. The elements A, B and C may be hand fed throughthe stitcher head until engaged by the driven presser roll unit, afterwhich the rolls draw the material through the stitcher head.

The sealing strip B is formed of a flowable solid elastomer having anunsized fabric strengthening member, such as cheese cloth, bonded to oneof its faces. In forming the scam, the needles pierce the elastomer andleave holes of considerable size around the threads, but these holes aresealed by the pressing action of the roll unit which flows the elastomeraround the threads so as tov complete the sealing of the seam.

It has been found that the needles I0 customarily used in tarpaulinstitching are of such alarge diameter that the presser roll unit cannotseal the needle holes without exerting an impractically large pressureupon the sealing strip. Accordingly, it is advisable to substituterelatively fine needles for those ordinarily used in tarpaulinmanufacture. In order to avoid breakage of the fine needles, they mustbe relatively short, and the needle shaft 1 must be adjusted downwardlyfrom its customary position.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, for some modifications will be obvious to those skilled inthe art.

I claim:

1. A fabric guide assembly adapted to be mounted immediately forward ofthe stitcher head of a sewing machine, comprising: a horizontal L-shapedmain plate, the outer corner of said L being mitered; guide means toretain a moving tape close adjacent one surface of said plate on thefirst arm of the L; a guide bar spanning said mitered corner wherebysaid movingtape may be guided around said corner to the second arm ofthe L adjacent the opposite surface of' said plate; a spacer platespanning said second arm of the L to form a tape take-off guide slottherewith; and guide means having upper and lower horizontal U-shapedfabric guide slots formed therein, one having its inner surface beneaththe second arm of the L and the other having its inner surface formed bysaid spacer plate, and said fabric guide slots having their open sidesoppositely disposed so that two'pi'eces of fabric may be guided to thestitcher head with their seam forming edge portions in overlappingrelationship and the tape therebetween.

2. A fabric guide assembly adapted to be mounted immediately forward ofthe stitcher head of a sewing machine, comprising: an L shaped separatorplate, said plate having its outer corner mitered and being providedwith guide 'elements'arranged to guide tape along a first arm of said Ladjacent a face of said plate, around said mitered corner and to thesecond arm of the L adjacent the opposite face of the plate; an integralspacermember spanning the second arm and forming a tape take-off guidetherewith, said spacer member having a lateral extension portion; asideguide member slidably secured to said lateral extension portion, forlateral adjustment with respect to said spacer member, said spacermember having a perpendicular face above one side of the take-off guide;a serpentine plate having an arm with a downturned edge portionextending beneath the take-off slot and a second arm overlying theside-guide member to form an upper fabric slot with the spacer member;and means on said serpentine plate whereby said serpentine plate islaterally adjustable with respect to the take-off slot.

3. Apparatus for forming a sealed lap sea-m comprising: a sewing machinehaving a stitcher head; a fabric guide assembly immediately forward ofthe stitcher head comprising, guide means having three superposed guideslots formed therein, the center slot being a tape slot closed on bothsides and the upper and lower slots being flat U-shaped slots with theiropen sides oppositely disposed, a tape lead-in guide including anL-shaped horizontal plate with the outer corner of the L mitered, afirst arm of said plate forming one face of said center slot a fiatguide loop extending across a second arm of said plate to guide a tapeadjacent a surface of said arm, a second flat guide element at saidmitered corner to guide tape around said corner and onto the oppositesurface of said first arm of said plate into said center slot; and apresser roll unit behind the stitcher head adaptedto draw the fabricfrictionally through the stitcher head and exert substantially uniformpressure upon all parts of a finished seam.

4;. Apparatus for forming a sealed lap seam comprising: a sewing machinehaving a stitcher head; a fabric guide assembly immediately forward ofthe stitcher head comprising, a horis zontal L-shaped main plate, theouter corner of 'said L being mitered, guide means to retain a movingtape close adjacent one surface of said plate on the first arm of the L,a guide bar spanning said mitered corner whereby said moving tape may beguided around said corner to the second arm of the L adjacent theopposite surface of said plate, a spacer plate spanning said second armof the L to form a tape take-off guide slot therewith, and guide meanshaving upper and lower horizontal U-shaped fabric guide slots formedtherein, one having its inner surface beneath the second arm of the Land the other having its inner surface formed by said spacer plate, andsaid fabric guide slots having their open sides oppositely disposed sothat two pieces of fabric may be guided to the stitcher head with theirseam forming edge portions in overlapping relationship and the tapetherebetween; and-a presser roll unit behind the stitcher head includinga driven roll and an idler roll' spaced therefrom,one of saidrollshaving its circumferential surface lightly scored to draw thefabric frictionally through the stitcher head and exert substantiallyuniform. pressure upon all parts of the finished seam. r

5. A fabric guide assembly adapted to be mounted immediately forward ofthe stitcher head of a sewing: machine comprising: guide means providinga pair of vertically spaced guide slots with oppositely facing opensides for guiding two pieces of fabric to the stitcher head withonlytheir adjacent edge portions in overlapping relationship andproviding a fiat tape slot to receive thick tape in a planar positionsandwiched between said guide slots; and a horizontal separator plateextending forwardly from said tape slot, said separator plate beingprovided with guide means whereby tape may be continuously fed to thetape slot and maintained out of contact with fabric entering either ofsaid super-- providing a pair ofvertically spaced guide slots withoppositely facing open sides for guiding two pieces of fabric to thestitcher head with only their adjacent edge portions in overlappingrelationship and providing a fiat tape slot to receive thick tape in aplanar position sandwiched between said guide slots, and a horizontalseparator plate extending forwardly from said tape slot, said separatorplate being provided with guide means whereby tape may be continuouslyfed to the tape slot and maintained out of contact with fabric enteringeither of said superposed slots until it is aligned with the tape slot;and means behind the stitcher head constructed and arranged to exertsubstantially uniform pressure upon all parts of a finished seam.

7. A fabric guide assembly adapted to be mounted immediately forward ofthe stitcher head of a sewing machine, comprising: guide means havingvertically spaced guide slots formed therein with oppositely facing opensides for guiding two pieces of fabric to the stitcher head with onlytheir adjacent edge portions in overlapping relationship; a guide memberhaving a flat tape slot formed therein to receive thick tape in a planarposition sandwiched between said guide slots; a forwardly extendinghorizontal separator plate having a first arm leading to said tape slotand a second arm disposed at an angle to the line of travel through saidslots; and guide means on said separator plate positioned and arrangedto guide a tape continuously from a tape supply located forwardly and toone side of said guide slots while keeping said tape out of contact witheither piece of fabric until it is alined with the tape slot.

8. A fabric guide assembly adapted to be mounted immediately forward ofthe stitcher head of a sewing machine, comprising: guide means havingthree superposed guide slots formed therein, the center slot being aflat tape slot to receive thick tape in a planar position, said slotbeing closed on both sides and the upper and lower slots being fiatU-shaped slots with their open sides oppositely disposed; a tape lead-inguide comprising an L-shaped horizontal plate with the outer corner ofthe L mitered, a first arm of said plate forming one face of said centerslot; flat guide elements extending across a second arm of said plate toguide a tape adjacent a surface of said arm; and a second flat guideelement at said mitered corner to guide tape around said corner and ontothe opposite surface of said first arm of said plate into said centerslot.

9. Apparatus for forming a sealed lap seam comprising: a sewing machinehaving a stitcher head; a fabric guide assembly immediately forward ofthe stitcher head comprising, guide means having vertically spaced guideslots formed therein with oppositely facing open sides for guiding twopieces of fabric to the stitcher head with only their adjacent edgeportion in overlapping relationship, a guide member having a flat tapeslot formed therein to receive a thick tape in planar positionsandwiched between said guide slots, a forwardly extending horizontalseparator plate having a first arm leading to said guide slot and asecond arm disposed at an; angle to the line of travel through saidslots; and guide means on said separator plate positioned and arrangedto guide a tape continuously to the tape slot from a tape supply locatedforwardly and to one side of said guide slots while keeping the tape outof contact with either piece of fabric until it is alined with the tapeslot; and a presser unit behind the stitcher head adapted to exert, substantially uniform pressure upon all parts of a finished seam.

10. The fabric guide assembly of claim 7 in which the guide means andthe guide member 8 are slidably connected for limited relative lateralmovement, and fastening means are providedv to secure said guide meansand said guide member firmly in any predetermined adjusted positions toadjust the relative positions of the closed side of one of the slots inthe guide means and the tape slot 11. The fabric guide assembly of claim10 in which the guide means includes an independently mounted portionhaving a vertical face which forms the side wall of one of the guideslots, said portion being mounted for. lateral sliding movement withrespect to the remainder of the guide means and the tape slot.

JOHN HERMAN.

REFERENCES CITED The following references are of record, in the file ofthispatent:

UNITED STATES PATENTS Number Name Date 642,344; Lipson Jan. 30, 19001,194,023 Hughes, Jr Aug. 8, 1916 1,575,453 Shutzer Mar. 2,, 19261,712,305 Leroy et al. May '7, 1929 1,906,104 Sailor Apr. 25, 19332,003,470 Rubel June 4,, 1935 2,278,043 Sailer Mar. 31, 1942

